Homes in rural areas are causing the greatest problems because paramedics often have only a house name to guide them.

In a bid to prevent life-threatening delays, families are now being urged to find out their six-figure map grid reference and keep it near the phone in case of emergencies.

Lee Washington, acting director of production and principal ambulance paramedic officer, said: "Emergency ambulance crews are increasingly reporting that they are encountering problems, particularly in the more rural parts of the county, with individual addresses, when all they have is a house name to help locate the patient's home.

"When responding to possible life threatening calls every second is vital. Any delay in getting to the patient may jeopardise that patient's life"

He appealed to all householders to check homes can be easily identified from the road, clearly marked and numbered and to ensure road signs outside their properties are not obstructed by shrubs.

Mr Washington added: "For rural locations I would further ask, perhaps as matter of some urgency, that householders obtain the six figure map grid reference of their property, and pass this to the ambulance service when they call.